Pipe joints

ABSTRACT

The invention relates to means and methods for rendering fire-safe, or more fire-safe, steel or like pipework which is lined with a plastic or like liner. At joints in such pipework, the liner is brought out over the flange face to form the actual seal. Consequently, the liner is vulnerable to fire or other forms of external heat at the joints. 
     In accordance with the present invention, a metal ring is provided around the periphery of the liner at each joint to protect the liner from fire. The metal ring is not intended to provide a complete seal if the seal between the liners should fail, but is does prevent any large escape of the contents of the pipework. 
     The ring may take various forms and may be, for example, a resilient ring of either U-section or M-section. Alternatively, the ring may be of flat-section and may slide on lips formed on inserts arranged between the flanges and the liners. These inserts may be arranged to provide the additional advantage of removing the need for special flange welding and machining.

This is a division of application Ser. No. 695,761, filed June 14, 1976,now Pat. No. 4,127,287 issued 11/28/78.

This invention relates to joints between pipe sections of the kind whichcomprise an outer metal pipe with an inner liner of rubber or syntheticresin material. Such pipes are used in the chemical and other industriesto combine the advantages of the mechanical strength of the metal pipewith the corrosion and contamination resistance of the lining material.

The term pipe section is used herein to include not only straightlengths of pipework, but also elbows, tees, crosses, valves and thelike.

When two sections of lined pipe are to be joined, it is the normalpractice to provide each pipe section with a metal flange and to arrangethe liner of each section so that it projects from the end of the pipebeyond the flange. The projecting portion of the liner is deformed sothat it is parallel with the flange faces and the two flanges are thendrawn together, for example, by means of bolts or the like, so that theflared outer portions of the liners form a seal between the twosections. Under normal circumstances, this arrangement ensures that thecontents of the pipework come into contact only with the liner. However,in the event of a fire, or any other form of exterior heating, theflared portions will be subject to an increased temperature and, sincerubber and synthetic resin materials generally have a lower meltingpoint than the metal used for the outer pipes, the liners may melt orotherwise disintegrate, so that the seal between the pipe sections isbroken. If the contents of the pipework are under pressure and areinflammable, they will be forced out through the joint and will providefuel for the fire. Alternatively, or in addition, if the contents of thepiping are corrosive or toxic, they will constitute a further hazard.

It is an object of the present invention to reduce the danger of largequantities of liquid being forced out of a joint between two pipesections when the joint is subjected to overheating.

It is a further object of the invention to provide a method of joiningpipe sections which is safer than the methods currently in use.

It is a further object of the invention to provide a secondary seal fora joint between the two pipe sections, which seal will reduce leakagefrom the joint in the event of failure of the primary seal.

From one aspect the invention consists in a joint between two pipesections, each of which includes an outer metal pipe and an inner linerof rubber or synthetic resin material, wherein metal jointing flangesare provid on the adjacent ends of the pipe sections, wherein the linerextends from the interior of each pipe section to form a liner extensioncovering a portion of the respective flange, and wherein means areprovided to urge the flanges towards one another so that a seal isformed between the mating faces of the two liner extensions, theimprovement which consists in providing a metal ring between theflanges, said metal ring covering the liner extensions to reduce leakagefrom the joint in the event of failure of the seal between the linerextensions.

From another aspect the invention consists in a method of forming ajoint between two pipe sections, each of which includes an outer metalpipe with an inner liner of rubber or synthetic resin material having anextension thereof projecting from the end of the pipe, said methodcomprising the steps of:

providing metal jointing flanges on the adjacent ends of the two pipesections;

deforming the extension of the liner of each pipe section so that itcovers a portion of the respective flange;

fitting a metal ring over the liner extension of one of said pipesections;

offering up the other pipe section to said one pipe section so that theliner extension of said other pipe section enters said ring; and

drawing the two flanges together to form a seal between the opposedfaces of the two liner extensions.

From yet another aspect the invention consists in a method of improvinga joint between two pipe sections, each of which includes an outer metalpipe with an inner liner of elastomeric material having an extensionflared over to provide a seal between the two sections, said improvementconsisting in the steps of:

opening the joint and separating the two pipe sections, fitting a metalring around the periphery of the liner extensions;

re-closing the joint with the metal ring in position.

Methods of performing the invention will now be described with referenceto the accompanying diagrammatic drawings, in which:

FIG. 1 is a sectional side view of a joint in accordance with theinvention,

FIG. 2 is a sectional side view of an alternative ring for use in ajoint as illustrated in FIG. 1,

FIGS. 3 and 4 are front elevations, partly in section, of furtheralternative rings for use in the joint illustrated in FIG. 1,

FIG. 5 is a sectional side view of a second embodiment of the invention,

FIG. 6 is a sectional side view of a third embodiment of the invention,and

FIG. 7 is a sectional side view illustrating one step in the formationof a joint of the kind shown in FIG. 5.

FIG. 1 shows a joint between two pipe sections 1 and 2 which consistrespectively of outer metal pipes 3 and 4 and inner liners 5 and 6. Theouter metal pipes may consist, for example, of steel, and the innerliners may consist, for example, of polytetrafluorethylene. A metalflange 7 is welded onto the end of the metal pipe 3 and a metal flange 8is welded onto the end of the pipe 4. The welds are shown, for example,at 9, 10, 11 and 12. After the welds 10 and 11 have been formed, theyare machined or ground so that a flat surface is formed on the end ofeach section. This flat surface consists, for example, of the raisedface 12 of the flange 8, the weld 11 and the end 13 of the pipe 6.

After the flat faces have been formed, the liners 5 and 6 are insertedin the metal pipes 3 and 4 with the portions projecting from the ends ofthe respective pipes. These projecting portions are then deformed toform flares as shown at 14 and 15.

A ring 16 consisting of spring steel, is placed over one of the flaresand the two pipe sections are then butted up together with the twoflares in contact and with the ring 16 in position around the flares asshown in FIG. 1. The flanges are then drawn together by means of nutsand bolts such as those shown at 17 and 18. It is, of course, to beunderstood that there will be four or more bolts arranged around theperiphery of the flanges in accordance with normal practice.

It is possible that, when the joint is first put into service, someliquid will seep out from the junction between the two flares 14 and 15.This liquid will then enter the channel 19 in the ring 16. To allow thisliquid to disperse, it is preferable that drain holes, such as thatshown at 20, should be provided in the ring 16. When the joint isactually in service, the nuts and bolts will normally be tightenedsomewhat further and this tightening will seal the joint so that nofurther liquid will escape under normal circumstances.

If a fire should occur in the plant which includes the joint asillustrated the ring 16 will prevent any flames from actually cominginto contact with the flares 14 and 15. Furthermore, the ring willprovide some degree of insulation to reduce the heat to which the flareswill be submitted. If, however the heat becomes so intense that thesynthetic resin material of the flares does commence to melt, thematerial will flow into the channel 19 and will block the drain holes20, thus increasing the protection provided by the invention for themain portion of the flares 14 and 15.

It is to be understood that the dimensions, strength, and resilience ofthe ring 16 should be such that the two legs 21 and 22 are urged againstthe faces of the two flanges when the bolts 17 and 18 have beentightened. On the other hand, the resistance to deformation of the ringshould not be sufficient to interfere with the normal tightening ofthese bolts. Further, it will be seen that the ring as illustrated hasan outer wall which is thicker than the two legs of the ring. Thisthicker outer wall is provided to prevent the flanges being drawn tooclose together in the event of the joint becoming bent, for example, asa result of excessive pressure on one side of the joint.

FIG. 2 shows an M-section ring 23 which may be used, if desired, inplace of the U-section ring 16 shown in FIG. 1, in order to provideadditional flexibility.

FIG. 3 shows a ring similar to that illustrated in FIG. 1 except that itis diametrically split to form two halves 24 and 25. A ring of this kindis particularly useful if it is desired to protect an existing joint bymeans of the present invention. Thus, an existing joint may be opened arelatively short distance and the two halves 24 and 25 inserted aroundthe periphery of the flared portions of the liner. When the bolts areretightened, the two halves will be held in position by the resilienceof the legs of the ring. Further, if by any chance excessive pressureshould develop as a result of a leakage occuring at the joint, the twohalves of the ring can only be separated a short distance before theyare held by the bolts such as those shown at 17 and 18 in FIG. 1.

In some instances, the space available between the periphery of theflared ends of the liners and the ring of bolts may be insufficient toaccommodate a ring of the desired size. In these circumstances, it willbe desirable to use a ring of the general kind shown in FIG. 4. In thiscase, the ring is provided with depressions such as those shown at 26and 27 in the outer wall of the ring to accommodate the respectivebolts. The left-hand side of FIG. 4 shows a ring 28 having a relativelythin outer wall 29 and, in this case, the depression 26 is formed bybending the outer wall inwardly as shown at 30. The right-hand half ofFIG. 4, on the other hand, shows a ring having a relatively thick wall31 and, in this case, the depression 27 is formed by removing materialfrom the outside of this wall.

As has already been explained in connection with FIG. 1, the normalmethod of forming a joint between two sections of lined pipe includesthe step of grinding the weld at the end of the pipe in order to providea flat face around which the liner can be bent to form the actual seal.In order to avoid the necessity for this grinding operation, it isproposed, in accordance with a feature of the present invention, toreplace the co-planar arrangement of the flange and the pipe end shownin FIG. 1 by a stepped arrangement as shown in FIG. 5. In thisembodiment, the flanges 7 and 8 are welded in position on the ends ofthe pipes 3 and 4 by means of welds 32, 33, 34 and 35. Since the flanges7 and 8 are welded on the ends of the respective pipes, the welds 33 and34 do not need to be ground. On the other hand, in order to provide therequired flat surfaces for supporting the liners 5 and 6, inserts 36 and37 are fitted within the flanges. These inserts include annular portions38 and 39 respectively, to provide support for portions of the linersco-axial with the pipes, and flat portions 40 and 41 to support theflare portion of the liners. Preferably, the inserts also include lips42 and 43 which engage the peripheries of the flare portions of theliners.

In this embodiment of the invention, the secondary seal for the joint isprovided by a flat-section ring or sleeve 44, which is a sliding fit onthe lips 42 and 43. The width of this ring is somewhat less than the gapbetween the two flanges 7 and 8 after they have been drawn together toform the seal by means of nuts and bolts (not shown). Thus, the ring 44does not interfere with the normal bolting-up of the joint.

In forming a joint as shown in FIG. 5, the adjacent ends of the two pipesections are initially prepared by the provision of the inserts 38 and39 and by deforming the liners 5 and 6 around the inserts to form theflared portions 14 and 15. Thereafter, the ring 44 is fitted over thelip of one of the inserts and the two sections are drawn together sothat the lip on the other insert enters the ring. As the bolts aretightened to draw the two flanges together, the second lip slides withinthe ring 44.

FIG. 7 illustrates one step in the formation of the joint shown in FIG.5. This figure shows the pipe 3 with the flange 7 welded in position onit and also shows the insert 38 in position. The liner 5 is shown in theprocess of being deformed by means of a tool 45, to form the flare 14.It is to be understood that the liner is deformed by a succession oftools such as that shown at 45, each successive tool having a largerapex angle so that it turns the flare through a larger angle.

It will be seen that the pipe 3 is shown as having a larger interiordiameter than the insert 38. This difference is exaggerated in thedrawing, but it is in practice found that the interior diameters ofpipes of any particular exterior diameter do vary by quite largeamounts. Accordingly, in practice, it is necessary to stock a largenumber of different tools of each particular apex angle, the noses 46 ofsaid tools having different diameters to suit the different interiordiameters of the pipes. Accordingly, it is an incidental advantage ofthe present invention that only one set of tools need be used for pipesof any one particular exterior diameter since the nose of the toolengages only the portion of the liner 5 within the insert 38. Thus,inserts can be manufactured with accurately diamensioned interiordiameters and can be used with pipes having varying interior diameters.

FIG. 6 shows that an embodiment of the invention generally similar tothat illustrated in FIG. 5 can also be used with joints in which theflanges are welded on the pipe ends with their raised faces flush withthe ends of the pipe. In this case, inserts 47 and 48 are used in placeof the insert 36 and 37, and it will be seen that they are generallysimilar, except that they do not include the annular portions 38 and 39.They do however, still include the flat portions 40 and 41 and lips 47and 48. It will be seen that these lips 47 and 48 differ slightly fromthe lips 42 and 43 of FIG. 5 in that they are chamfered to assist in thefitting of the ring 44. It is of course, to be understood that thischamfered arrangement could be provided equally on the inserts 36 and 37of FIG. 5.

It will be understood that the invention provides a method of makingfire-safe or more fire-safe, steel or like pipework which is lined witha rubber, plastic or like liner. The additional ring which is providedin accordance with the invention protects the rubber or plastic flaresbetween the flanges and prevents any large flow of the contents of thepipework from a damaged joint.

The rings can be readily fitted either to new joints or to existingjoints, and can be supplied in a range of widths to suit most variationsin liner thicknesses. In the case of the resilient type of ring, thelegs should be compressed when the rings are fitted, but the outer thickwall section should be clear of the flanges. In the case of the slidingring, the insert holds the ring loosely, but firmly, in place.Furthermore, the use of an insert removes problems relating tovariations in bore sizes of the pipework when flaring or like tools areused to enter the ends of the pipes. The inserts can be manufacturedwith similar bore sizes so that, over the length of the socket on thetool that enters the pipe, the bores will be virtually constant,removing the need for different tool sizes.

Although specific apparatus has been shown for the purpose of describingapplicant's invention, it will be apparent by those skilled in the arethat other variations and modifications in the specific structureillustrated may be made without departing from the spirit and scope ofthe present invention which is limited only to the appended claims.

What is claimed is:
 1. In a joint between two pipe sections, each pipe section being of the type including an outer metal pipe and an inner liner of rubber or synthetic resin material, wherein metal jointing flanges are provided on the adjacent ends of the pipe section, and wherein each liner extends from the interior of its associated pipe section radially outwardly to form a liner extension between portions of the respective flanges and terminating in generally annular surfaces, the joint including means for urging the flanges towards one another so that a seal is formed between the mating faces of the two liner extensions lying between the flange portions, the improvement comprising an annular metal ring between substantially planar, parallel faces of the jointing flanges and radially outwardly of the liner extensions, and first and second generally annular metal inserts, each of said inserts having a portion lying between one of said flanges and one of said liner extensions, each of said inserts further including an axially protruding peripheral lip forming sliding sealing contact with an inner surface of said annular ring such that the combination of said metal inserts and metal ring reduces leakage from the pipe joint in the event of failure of the seal between said liner extensions as a result of external fire.
 2. A joint according to claim 1, wherein each of said inserts includes an annular portion located radially inwardly of the respective flange.
 3. A joint between two pipe sections, each of which includes an outer metal pipe and an inner liner of corrosion-resistant material, wherein metal jointing flanges are welded on the adjacent ends of the pipe sections with a portion of each flange projecting beyond the end of the respective pipe section, and wherein an insert is provided within each flange, the joint further comprising means for urging the flanges toward each other, said insert comprising an annular portion located radially inwardly of the respective flange, a disc-like portion in contact with the outer face of the flange and peripheral lip located radially outwardly of the disc-like portion, wherein the liner extends from the interior of each pipe section to form a liner extension covering said disc-like portion of the respective insert, wherein the flanges are urged towards one another so that a seal is formed between the mating faces of the two liner extensions, and wherein an annular metal sleeve is slidably located and sealingly engaged on the lips of said two inserts such that the combination of said metal inserts and metal ring reduces leakage from the pipe joint in the event of failure of the seal between said liner extensions as a result of external fire. 